Determining which carb is leaking

[tom203]

This is an interesting idea. So I would take off the air filter cover, remove the air filter cage, stick a rectangular piece of cardboard through the hole into the carb section of the airbox. Put the airbox back together and then go for a quick ride (so the cardboard doesn't get saturated) and see if there's spots under a certain carb?

That was my plan!

[Souske]

You mean without the airbox / using pods? I'd love to, not for any performance reasons but because I can't stand removing/re-fitting the carbs (allegedly it's a tighter fit on the 550 model). However, I've read on here that it makes it much harder to get the bike running right. Since I don't really know what I'm doing, I'd like as few variables as possible.

Makes sense, I am using pods because that is what my bike came with. It used to pee so much gas it would drip from the pods while running. Changed the inlet needles/seats/orings on offending carbs and no more leaking.

Good luck on the cardboard method, sounds like a good idea!

[scott]

Well, I put a strip of cardboard in the airbox. I actually had to cut it into 2 pieces to get it to fit - that air filter hole isn't as big as I thought, I couldn't' fit my hand in there too easily. It didn't look like it moved though during the ride. I took a short ride (idled on choke for maybe 3 mins, rode it for maybe 5 mins) and here's the results.

The top of the cardboard (facing the carbs/holes):


The bottom of the cardboard (laying on the airbox "floor"):


Perhaps the bottom is wet from where it collected on the sides? I was thinking the sides of the airbox were higher than the middle but maybe not.

I did try to dry out the airbox before putting in the cardboard strip. It seemed like it was a little oily but not wet. I didn't knock myself out drying it though so it's possible that was already wet but I don't think so. Also, it had been 24 hrs since the bike was run previously if that means anything.

Based on the top of the strip, it seems like it's coming out of ALL the carbs to varying degrees! Carb #1 and #2 seem worse. Would the mixture and/or synch have anything to do with this? Would a rich mixture cause this or idling too long on choke

[tom203]

Well, I put a strip of cardboard in the airbox. I actually had to cut it into 2 pieces to get it to fit - that air filter hole isn't as big as I thought, I couldn't' fit my hand in there too easily. It didn't look like it moved though during the ride. I took a short ride (idled on choke for maybe 3 mins, rode it for maybe 5 mins) and here's the results.

The top of the cardboard (facing the carbs/holes):


The bottom of the cardboard (laying on the airbox "floor"):


Perhaps the bottom is wet from where it collected on the sides? I was thinking the sides of the airbox were higher than the middle but maybe not.

I did try to dry out the airbox before putting in the cardboard strip. It seemed like it was a little oily but not wet. I didn't knock myself out drying it though so it's possible that was already wet but I don't think so. Also, it had been 24 hrs since the bike was run previously if that means anything.

Based on the top of the strip, it seems like it's coming out of ALL the carbs to varying degrees! Carb #1 and #2 seem worse. Would the mixture and/or synch have anything to do with this? Would a rich mixture cause this or idling too long on choke

What, nobody is leaping to a conclusion? Short ride like that, it seems they are all spitting back into airbox. I doubt it's the choke, cuz in normal ride, it's off and any excess fuel would be sucked in as the bike ran and you wouldn't find it. It has to be spraying out carb throats or thru air jet orifice - but that takes back pressure of some sort.

[scott]

What, nobody is leaping to a conclusion?

Yeah - I figured there'd be some interpretations of my little Rorschach test.

Short ride like that, it seems they are all spitting back into airbox.

So basically, even a little spitting back into the airbox is indicative of a problem?

I doubt it's the choke, cuz in normal ride, it's off and any excess fuel would be sucked in as the bike ran and you wouldn't find it. It has to be spraying out carb throats or thru air jet orifice - but that takes back pressure of some sort.

That sounds like something would impact all the carbs which seems to match the symptoms. What can create back pressure?

[tom203]

Yeah - I figured there'd be some interpretations of my little Rorschach test.


So basically, even a little spitting back into the airbox is indicative of a problem?


That sounds like something would impact all the carbs which seems to match the symptoms. What can create back pressure?

I'm going to go way out on a limb here. IF ( and this is big IF ), the intake cam was off by one tooth, then the intake valves would not be closed soon enough as spark ignited. This would result in back pressure thru carbs, especially at lower speeds; it would be less a problem as rpm's went up as the carbs are moving air/fuel mixture quicker and it's harder for the flow to reverse due to momentum. Now , I will get another beer!

[scott]

I'm going to go way out on a limb here. IF ( and this is big IF ), the intake cam was off by one tooth, then the intake valves would not be closed soon enough as spark ignited. This would result in back pressure thru carbs, especially at lower speeds; it would be less a problem as rpm's went up as the carbs are moving air/fuel mixture quicker and it's harder for the flow to reverse due to momentum.

Hmm - that doesn't sound good. Is that something I could have messed up doing the valve adjustment?

Not sure if this is useful or related but on a ride today, it started getting a very low idle / stalling at idle. This happened a few weeks ago on a very hot day (I wasn't sure if the temperature was a factor). It wasn't hot today but I was riding at 50+ MPH for a bit. I pulled over and tried to adjust the idle screw but it didn't seem to make a difference. I basically had to hold the throttle on slightly while waiting for lights to change to keep it from stalling but I made it home at least. I tried starting it up to see about tweaking the idle screw and it wouldn't stay idling so I just let it sit. Several hours later it did start with the choke. I'll have to revisit the idle screw adjustment the next time I get the bike warmed up.

Since people always mention the petcock (even though mine is a practically new OEM model), I took off the tank and tested it to rule that out. No fuel by default, fuel when the prime screw is loosened, fuel when I suck on the vacuum hose. I tried blowing on the vacuum hose at first but that didn't do anything. So, the petcock seems fine.

I also tried checking the voltage drop between the battery and the coil connectors (taking stabs at things to test). With the key on, the drop was ~1.5V at one connector, and ~0.5 V at the other. I wasn't sure how to test it with the connectors attached to the coil. I was kind of surprised it was different at the 2 coils though. From what I've read, this voltage drop could get worse when hot which may relate to my low idle / stalling issue. I should have measured this right when I got home I guess. Since the fuel in the airbox isn't dependent on the engine being very warm, I'm guessing it's not related.

Now , I will get another beer!

Enjoy - thanks for all your help!

[cowboyup3371]

How many turns out are your mixture screws?

[scott]

How many turns out are your mixture screws?

I started at 3 turns out and tweaked from there. I didn't note how much I turned each mixture screw from 3 though. I wasn't able to get a noticeable change on some of the carbs so I wasn't positive I got it right.

I'll try resetting them today when I do the idle adjustment after I get the bike warmed up on a short ride. Are you thinking I have a rich condition? Other than smelling gas (like when the choke is on), I'm not sure how a rich vs lean condition behaves.

Maybe I should bite the bullet and get a Colortune. At this point, I'm not sure if I have serious problems with the bike though (see possible intake cam issue mentioned above) so I'm hesitant to spend a lot of money.

[cowboyup3371]

Yours sounds more lean than anything much like what mine did.

[scott]

Yours sounds more lean than anything much like what mine did.

Oh! I guess I'll try them at more than 3 turns out. I would think making it richer would cause more fuel to go to the airbox but I wouldn't know.

I tried to re-do the vacuum synch (homemade manometer with bottles of water, tubes, etc.). It never seems to work quite like it's supposed to - I wind up having to tweak all the adjusters. When I try to do the Carb 2/3 adjuster, then 1/2, then 3/4, it never seems to work. It always seems to throw the Carb 2/3 out of synch and I have to go back and forth to all of them (as opposed to setting Carb 2/3 and leaving it).

I got them close - to the point where water wasn't being pulled by any carb. I wouldn't say it was idling super-smooth. I couldn't really drop the RPM to 900 to do the Highest RPM mixture setting. Also, revving the engine would show the carbs were not in synch at higher RPMs but I assume that's not unusual. And of course, it was dripping fuel out the airbox during this.

I'll take another stab at the vacuum synch / mixture screw setting.

[scott]

And of course, it was dripping fuel out the airbox during this.

Correction, I assumed it was fuel because that's what has been dripping out of the airbox after rides. It actually seems more like dirty water is dripping out of the airbox during the vacuum synch. Huh? Water isn't being sucked into the vacuum ports, but maybe condensation from the bottles is? Is this hurting anything or indicative of something?

[tom203]

Correction, I assumed it was fuel because that's what has been dripping out of the airbox after rides. It actually seems more like dirty water is dripping out of the airbox during the vacuum synch. Huh? Water isn't being sucked into the vacuum ports, but maybe condensation from the bottles is? Is this hurting anything or indicative of something?

So during this homemade vacuum synch, water is finding it's way to airbox? This can only be from your synch setup and still means that some pressure is forcing air/gas/water back thru carbs throats- wrong direction! When you did your valves, did you have to go change shim thicknesses by a large margin on intake side? I don't think this is an electrical problem and an idle stop screw that appears to do nothing still points to a mixture problem. Is this a new-to-you bike or an old friend?

[scott]

So during this homemade vacuum synch, water is finding it's way to airbox? This can only be from your synch setup and still means that some pressure is forcing air/gas/water back thru carbs throats- wrong direction!

Yes - condensation seems like the only possibility (water boiling in the bottles I guess). I definitely didn't see water going up the vacuum hoses - it really shouldn't be possible unless all the water went into 1 bottle which I didn't let happen.

When you did your valves, did you have to go change shim thicknesses by a large margin on intake side?

Here's my shim changes on the intake side (my exhaust valves had larger shim changes).
[CODE]
Position Original (Shim; Clearance) Current (Shim; Clearance)
IN #1 2.64mm; < 0.04mm 2.59mm; 0.08mm
IN #2 2.67mm; 0.05mm 2.61mm; 0.10mm
IN #3 2.70mm; 0.05mm 2.67mm; 0.08mm
IN #4 2.58mm; 0.05mm 2.56mm; 0.08mm
[/CODE]

I don't think this is an electrical problem and an idle stop screw that appears to do nothing still points to a mixture problem.

Just to clarify, my idle adjustment screw normally has an effect. It was just when I had the low idle/stalling at idle problem the other day, adjusting the screw had no effect / didn't prevent it from stalling. Today when trying to do the synch, the idle screw definitely did something.

Is this a new-to-you bike or an old friend?

New-to-me in Feb/March (my first bike). Obviously I am very inexperienced with this stuff so I really appreciate the help. The bike has < 8K miles but I don't know much about its history.

[tom203]

Yes - condensation seems like the only possibility (water boiling in the bottles I guess). I definitely didn't see water going up the vacuum hoses - it really shouldn't be possible unless all the water went into 1 bottle which I didn't let happen.



Here's my shim changes on the intake side (my exhaust valves had larger shim changes).
[CODE]
Position Original (Shim; Clearance) Current (Shim; Clearance)
IN #1 2.64mm; < 0.04mm 2.59mm; 0.08mm
IN #2 2.67mm; 0.05mm 2.61mm; 0.10mm
IN #3 2.70mm; 0.05mm 2.67mm; 0.08mm
IN #4 2.58mm; 0.05mm 2.56mm; 0.08mm
[/CODE]


Just to clarify, my idle adjustment screw normally has an effect. It was just when I had the low idle/stalling at idle problem the other day, adjusting the screw had no effect / didn't prevent it from stalling. Today when trying to do the synch, the idle screw definitely did something.

New-to-me in Feb/March (my first bike). Obviously I am very inexperienced with this stuff so I really appreciate the help. The bike has < 8K miles but I don't know much about its history.

You're gaining experience ! You did the valve adjustment (and kept a record!), so you're doing fine. However, with an unknown bike history, there's new stuff to explore. This spitting into airbox is strange- you've correctly ruled out petcock-, so I think you have to check the camshaft to crankshaft timing, just in case someone screwed up. I recall seeing info maybe on a link from Basscliffs, but I haven't done this myself yet. It involves putting the crankshaft on TDC and making sure both camshafts are in correct position- this likely means counting chain links between intake and exhaust camshafts. Hopefully someone with experience will chime in and explain. It would be nice to rule this out as a problem.